Slack brings all your communication together in one place. It's real-time messaging, archiving and search for modern teams. Create open channels for the projects, groups and topics that the whole team shares. Slack searches whole conversations, not just individual messages, so you can find what you’re looking for no matter who said what or when they said it. Slack free open-source (self-hosted) alternatives are: Mattermost, Rocket.Chat, Zulip

Comparing Cisco Spark vs Slack is like comparing apples to oranges. Because your business is unique and nobody except you can decide, which is better for your company. But we can add some fun to your research and suggest some new comparison parameters.

Ok, now let's compare the UI. Looks like Cisco Spark has more user-friendly interface than Slack because it's bigger. At least on our screenshots

To compare the popularity of the solutions we counted how many alternatives people search for each of them on the Internet. And it turns out that Slack is more popular than Cisco Spark

Slack, the workplace communication service, acquired Screenhero, a screen-sharing tool for teams, with plans to incorporate its features. Screenhero provides a range of collaboration tools, including voice chat, faster screen sharing between individuals and the option to have multiple mouse cursors interacting over various applications. The startup's six-person team will join Slack, and work to integrate and advance those features there. The Screenhero acquisition is Slack's second to date. It bought Spaces, a small startup also developing collaboration tools, in September.